Repaglinide (+) 2 ethoxy-4[N-{1-(2-piperidinophenyl)3-methyl-butyl}aminocarbonyl methyl]benzoicacid of formula 2 is from a class of hypoglycemic agents for type II non insulin dependant diabetes mellitus Hitherto known process for the preparation of (RS) 3-methyl-1-(2-piperidinyl phenyl butyl amine having formula 1 involves two methods as shown below
Route 1 (J. Med. Chem. 1998, 41, 5219)
                a. Heating a mixture of 2-halo bezonitrile, piperidine, and N-formyl piperidine at 160–170° C. to obtain 2-piperidino benzonitrle of formula 3.        
                b. Grignard reaction: The reaction of i BuMgBr with 2-piperidino benzonitrile in THF solvent to obtain (3-methylbutyl)-(2-piperidino-phenyl)-ketimine having formula 4.        
                c. Hydrogenation of (3-methylbutyl)-(2-piperidino-phenyl)-ketimine of formula 4 in methanolic ammonia in presence of raney nickel at 80 C for 6 hrs to obtain (RS) 3-methyl-1-(2-piperidinyl phenyl butyl amine having formula 1        
Route 2.                a. Heating a solution of 2-piperidino benzonitrile of formula 3 in formic acid in the presence of raney nickel to obtain 2-piperidino benzaldehyde of formula 5.        
                b. Hydrogenation of o-piperidino benzaldehyde of formula 5 in methanolic ammonia in the presence of raney nickel to obtain 2-piperidino benzylamine of formula 6.        
                c. Condensation of 2-piperidino benzylamine of formula 6 with 2-piperidino benzaldehyde of formula 5 to obtain N-(2-piperidinobenzyl)-2-piperidino benzaldimine of formula 7.        
                d. Alkylation of N-(2-piperidinobenzyl)-2-piperidino benzaldimine of formula 7 with 2-methylallyl chloride in presence of base i.e LDA to obtain (RS) 3-methyl-1-(2-piperidinyl phenyl) butyl amine having formula 1        
The prior art processes have following drawbacks.                1. Condensation of piperidine requires higher temperature.        2. Reduction of ketimine requires autoclave which is inconvenient on industrial scale.        3. The use of strong base i.e LDA reagent requires −80° C. which is also inconvenient on industrial scale.        